The present invention relates to the deposition of organic material through a mask onto a substrate in the process of making an organic light emitting diode (OLED).
In the making of organic light emitting devices (OLED) there are a number of steps in which organic layers are deposited on or over a substrate. It is essential that a deposition mask be aligned and properly mounted so that accurate deposition takes place. The deposition mask is typically a precision mask made of a magnetic material and is thin and malleable. The deposition mask is lithographically patterned and because it is thin permits the appropriate thickness of organic material to be deposited on or over the substrate. The maximum size of a single piece depositions mask is limited by manufacturing process limitations, specifically dimensional accuracy and overall size. Another limitation of the present technology is the inability to replace damaged areas of the deposition mask. The deposition mask manufacturing process is subject to error and the increase in size and complexity of a mask design account for lower yield when manufacturing deposition masks. There is a need for more accurate, larger format precision deposition mask. There is also a need for a method of replacement of defective areas of the deposition mask.
It is an object of the present invention to increase the throughput of forming OLED devices which use deposition masks.
It is a further object of the present invention to provide a structure which will permit the simultaneous formation of organic layers of an OLED device through different mask segments.
These objects are achieved in an alignment and holding device for permitting a deposition mask having a plurality of magnetic mask segments to be mounted to a frame for positioning relative to a substrate to facilitate simultaneous deposition of organic material on to the substrate which will be part of an organic light emitting device, comprising:
(a) a base having a first set of alignment pins and a second set of alignment pins;
(b) two or more plates segments (four depicted) secured to the base;
(c) a frame having two or more openings (four depicted) aligned with the plates segments, the frame having a plurality of magnets magnetic cross bars located in cross bar receiving channels being formed with a first set of alignment pin receiving holes corresponding to the position of the first set of pins so that the frame is removably mounted to the base;
(d) a plurality of magnetic mask segments positioned on the plate to define the deposition mask;
(e) a transparent flat plate contacting the second set of alignment pins and the magnetic mask segments and being sized to expose portions of segments of the magnetic mask segments;
(f) means of securing mask sections to perimeter of the frame in the exposed areas;
(g) means for securing the magnetic mask segments to the cross bars of the frame via the cross bar channel and magnetic cross bars.
These objects are also achieved by a method of aligning a plurality of masks segments to form a deposition mask which permits a more effective manufacture of organic light emitting diode devices, comprising the steps of:
(a) providing a base having a first and second set of alignment pins and securing two or more plates segments to the base;
(b) providing a frame having central openings aligned with the plates segments and formed with a first set of alignment pin receiving holes;
(c) aligning the frame and base by positioning the first set of alignment pins in the first set of alignment pin receiving holes;
(d) positioning the plurality of magnetic mask segments on the plates segments and frame;
(e) providing a transparent flat plate aligned with the second set of alignment pins on the plurality of magnetic mask segments, such transparent flat plate having fiducial marks;
(f) positioning the magnetic mask segments to be properly aligned with the fiducial marks and securing the magnetic mask segments to the frame; and
(g) magnetically securing the plurality of magnetic mask segments to the frame using magnetic cross bars bonded in cross bar receiving channels cross bars providing an assembled deposition mask with each magnetic mask segment being adapted to be used in the deposition of organic material on a single substrate.
It is a feature of the present invention that by mounting and securing magnetic mask segments using a plurality of magnets magnetic cross bars a mask can be produced that provides improved dimensional accuracy of a deposition mask having the ability to remove and replace mask sections. The present invention makes possible the manufacture of a larger format deposition mask.
An advantage of the present invention is that the deposition magnetic mask sections can be accurately assembled and mounted to a frame that is then positioned relative to the substrate. Magnetic mask segments can be held in place magnetically to make a mask assembly larger than is capable with single piece deposition mask. An assembled deposition mask can be disassembled to allow for removal of defective magnetic mask segments. The magnetic mask segments can then be replaced. An assembled deposition mask being made up of small segments are less expensive to produce. Assembled deposition masks have greater life expectancy, being repairable. An assembled deposition mask has greater accuracy than present single piece deposition masks (of similar size). This approach will improve yield and make possible deposition of larger substrates.